Piston for fluid-pressure engines



y 2, 1929- P. K. SAUNDERS 1.719.727

PISTON FOR FLUID PRESSURE ENGINES Filed Jan. 10, 1929 R I Irrewtaf: 10 1 19 7 M Pfiilift 7ftffi salqvders, 16 I I By 7 16 Patented July 2, 1929.

UNITED STATES 1,719,727 PATENT OFFICE.

PHILIP KEIlITH SAUNDERS, 01 J OHANNESBURG, SOUTH AFRICA.

PISTON FOR FLUID-PRESSURE ENGINES.

Application filed January 10, 1929, Serial No: 331,597, and in Great Britain December 10, 1928. i

This invention relates to pistons for fluid pressure engines of the kind having a skirt of a hard wearing metal, such as steel, attached on itsnon-pressure sides only to depending lugs integral with a crown castpreferably in a metal of good heat conductivity, such as aluminium alloy.

Its chief object is to provide a construction in which the skirt and its attachment tothe crown will adequately resist the stresses to which they aresubjected due to mechanical loading, inertia stresses and the effects arising from the'different co-e'lficients of expan sion of the two metals.

Inthe accompanying drawings,

Figure 1 is aside elevation, half in central section, showing one form of-complete piston constructed in accordance with this invention.

Figure 2 is a plan of the same partly in section on the line IIII of Figure 1 and showing at 13 the cylinder bore.

Figure 3 is aside view, partly in section, of a skirt used inthe construction shown in Figures 1 and 2 looking at a non-pressure face.

Figure 4 is a side elevation of a modified form of skirt, and

Figure 5 is a horizontal section of the same, showing at 13 the cylinder bore,

Like numerals indicate like parts throughout the drawings.

In the construction shown in Figures 1, 2 and 3, the piston crown 2 has at each side a depending lug 3 which is thickest and strongest near its attachment to the crown, to which it is also webbed as shown at 4. In each depending lug is a boss 5 for the reception of the gudgeon pin 6. The crown and lugs are produced as a casting preferably of some metal having a high heat conductivity, such as aluminium alloy, though cast iron may be used, and it is provided with grooves to take the piston rings 8.

The skirt 9 is of a hard wearing material such as steel, and it is preferably very thin and produced by a pressing or similar process. On the two pressure faces, that is to say, the faces which transmit the pressure due to the angularity of the connecting rod, it is provided with one or more corrugations or grooves 10 which serve to stiffen those faces and also to retain lubricant. The top and bottom edges of the pressure faces may also be rounded or flanged as shown at 11. The result of these grooves and flanges is that the skirt is comparatively stiff on the pressure faces, but on the non-pressure faces as at 12 1t is relatively more flexible, and

these parts are flattened and are purposely clear of the cylinder wall, the outline of which is indicated at 13.

These non-pressure faces of the skirt are formed with inwardly projecting portions such as 1stand in the construction illustrated in Figures 1 to 3 these walls 14 are connected together by the part 15, the construction at this point being that of a longitudinal channel on each non-pressure face. In the base of this channel are formed one or more apertures 16 below the gudgeon pin hole 21 and notches at 17 and 18, the horizontal edges of these notches and of the hole 16 being left buried or with tongues 19 which are bent over as is shown in Figure 1. There may also be a notch 20 (Figure above the gudgeon pin hole, but the edge of this is preferably out clean and not bent over.

The skirtso constructed is placed inamould, and the crown portion with its depending lugs 3 is cast on to it, so that the only attachment of the skirt to the crown portion is through the depending lugs which are'secured only to the non-pressure faces of the skirt.

As the head expands, these lugs tend to move apart, which merely distorts slightly the flexible non-pressure faces 12 without affecting the shape of the pressure faces. The cylindrical contact of these faces with the cylinder walls is therefore always maintained, which is a very important feature. As the non-pressure faces 12 approximate to straight lines, movement of the depending lug towards and away from one another as the crown varies in temperature has little or no effect upon the pressure faces of the skirt and therefore its clearance in the cylinder remains practically constant and the piston operates quietly at all times.

The inwardly projecting portions laconstitu'te substantial lateral buttresses to transmit the side thrust due to mechanical loading, and the tongues 19 provide adequate axial support, in addition to the keying effect of the cast metal traversing the holes 16 and the notches, which prevents the skirt and crown working loose owing to the inertia stresses. Furthermore, by leaving the edges of the notches 2O sharp and not tongued, the part of the skirt above the gudgeon pin can cut into and elongate its engagement with the cast crown, if, necessary, on account of the relative movement of the skirt and crown owing to the different co-eflicients of expansion of the two metals and the length of the attachment.

Alternatively the skirt may be formed as shown in Figures 4 and 5. Here, the nonpressure faces 12 are, as before, intended to be clear of the cylinder walls 13, and both above and below the hole 21 for the gudgeon pin slots 22 are pierced in the skirt, the metal displaced being bent inwards to form inwardly projecting curved tongues 23. When the head is cast on to the skirt the metal will traverse the apertures 22 and the bent tongues will constitute substantial mechanical keying devices which ensure the necessary lateral as well as longitudinal rigidity.

The invention thus provides a simple and effective means for uniting the skirt and crown in a manner which takes care of all the stresses and does not permit the expansion and contraction of the head to interfere with the fit of the skirt in the cylinder.

hat I claim as my invention and desire to secure by Letters Patent of the United States is 1. In a piston, the combination with a sheet metal skirt the pressure faces of which are stiffer than the non-pressure faces, of a crown with depending lugs which are cast on to the non-pressure faces of the skirt thereby constituting; the sole connection between said crown and said skirt.

2. In a piston, the combination of a sheet metal skirt the pressure faces ofwhich are stiffer than the non-pressure faces inwardly projecting portions to said non-pressure faces, and a crown having at each side a depending lug which are cast on to said nonpressure faces and on to said inwardly pro jecting portions to constitute the sole connection between said crown and said skirt.

3. In a piston, the combination of a sheet metal skirt the pressure faces of which are stiffer than the non-pressure faces, inwardly projecting portions to said non-pressure faces, tongued apertures in said inwardly projecting portions, and a crown having at each side a depending lug which are cast on to said non-pressure faces and on to. said inwardly projecting portions to constitute the sole connection between said crown and said skirt.

4:. In a piston, the combinationv of a sheet metal skirt the pressure faces of which are stiffer than the non-pressure faces, the latter being clear of the cylinder bore, a longitudinal channel in each of said non-pressure faces, apertures in said channels, bentover tongued edges to said apertures, and a crown having two depending lugs which are cast on to said non-pressure faces the metal of the lugs traversing the apertures, substantially as set forth.

5. A piston as claimed in claim 4, in which the apertures with bent-over tongued edges are made only on one side of-the gudgeon pin and plain apertures made on the other side thereof.

In testimony whereof I have signed my name to this specification.

' PHILIP KEITH SAUNDERS. 

